Metric conduit taps are all 1.5 mm pitch, but is eg a 16mm conduit tap the same as a standard M16 x 1.5 mm tap?
A 16 x 1.5 mm tap (with another useful tap) went for £2.00 on Ebay this afternoon, and a 16 mm "electricians" conduit tap went for £8.00 a few minutes after.